1, 25-D3 Protects From Cerebral Ischemia by Maintaining BBB Permeability via PPAR-γ Activation

A systematic review and meta-analysis of the linkage between low vitamin D and the risk as well as the prognosis of stroke

OBJECTIVE

The research intended to probe the connection between the risk of stroke and serum vitamin D levels.

METHODS

Three electronic databases (Cochrane Library, EMBASE, PubMed) were searched according to the subject terms from inception until July 29, 2022, and retrieved researches were screened on the basis of inclusion and exclusion criteria. Two investigators conducted the quality assessment and data extraction. Using Stata 16.0 software, a meta-analysis was conducted on the extracted data.

FINDINGS

In total, 27 studies with 45,302 participants were included. Among these studies, 20 focused on stroke risk, while 7 examined stroke prognosis. According to the meta-analysis findings, it was observed that a higher stroke risk is connected to reduced levels of serum vitamin D. This association was reflected in a combined relative risk (RR) of 1 .28 (95% confidence interval (CI): 1.15-1.42) and a worse prognosis after stroke (RR = 2.95, 95% CI: 1.90-4.60). Additional analysis indicated that no apparent relationship between a decrease in vitamin D and the probability of experiencing a hemorrhagic stroke was found. The RR found was 1.93 (95% CI: 0.95-3.95). On the other hand, it was observed that a reduction in serum vitamin D levels was linked to an elevated likelihood of developing an ischemic stroke. The RR identified was 1.72 (95% CI: 1.78-2.03). Moreover, a lower level of vitamin D in the bloodstream was associated with a more unfavorable prognosis for individuals who suffered from a stroke. The RR for this correlation was 2.95 (95% CI: 1.90-4.60). However, further research is required to confirm the above-mentioned findings.

CONCLUSION

In conclusion, lower concentration vitamin D was found to be related to an increased risk of stroke, which could mainly be reflected in ischemic stroke patients but not in patients with hemorrhagic stroke. A lower serum vitamin D level was correlative with the poor prognosis of stroke.

Vitamin D and ischemic stroke - Association, mechanisms, and therapeutics

Confronting the rising tide of ischemic stroke and its associated mortality and morbidity with ageing, prevention and acute management of ischemic stroke is of paramount importance. Mounting observational studies have established a non-linear association of vitamin D status with cardiovascular diseases, including ischemic stroke. Paradoxically, current clinical trials fail to demonstrate the cardiovascular benefits of vitamin D supplementation. We aim to update recent clinical and experimental findings on the role of vitamin D in the disease course of ischemic stroke, from its onset, progression, recovery, to recurrence, and the established and alternative possible pathophysiological mechanisms. This review justifies the necessities to address stroke etiological subtypes and focus on vitamin D-deficient subjects for investigating the potential of vitamin D supplementation as a preventive and therapeutic approach for ischemic stroke. Well-powered clinical trials are warranted to determine the efficacy, safety, timing, target individuals, optimal dosages, and target 25OHD concentrations of vitamin D supplementation in the prevention and treatment of ischemic stroke.

A Case Study of Vitamin D Supplementation Therapy and Acute Respiratory Tract Infection

BACKGROUND

Low serum concentrations of 25-hydroxyvitamin D correlate with higher susceptibility to acute respiratory tract infections (ARTIs). The case study presented here aims at sheding light on the correlation between vitamin D levels, the vitamin D supplement dose, and the incidence of ARTIs.

CASE REPORT

A 23-year-old female patient with a vitamin D insufficiency was able to successfully increase her vitamin D levels from 45.60 nmol/l to 85.91 nmol/l (reference ranges 75-200 nmol/l) through the use of supplements. However, it was surprising to observe a decrease in vitamin D levels even though the patient continued taking supplements. Further examination indicated that the patient was experiencing common symptoms of an acute respiratory tract infection (ARTI). This case highlights the intricate connection between ARTIs and vitamin D intake.

CONCLUSION

This case study clearly demonstrates the intricate connection between vitamin D levels, supplement treatment, and ARTIs. The observed decrease in vitamin D levels during the course of supplementation, while the patient was suffering from an ARTI, suggests that respiratory infections may affect vitamin D metabolism.

Else_BRB_110660Docosahexaenoic acid promotes M2 microglia phenotype via activating PPARγ-mediated ERK/AKT pathway against cerebral ischemia-reperfusion injury

In ischemia-reperfusion stroke, microglia play a dual role in brain injury as well as brain repair, and promoting their switch from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype is considered to be a potential therapeutic strategy. Docosahexaenoic acid (DHA) is an essential long-chain omega-3 polyunsaturated fatty acid that exhibits potent anti-inflammatory properties in the acute phase of ischemic stroke, but its effect on microglia polarization is unknown. Thus, the objective of this study was to investigate the neuroprotective effects of DHA on rat brain following ischemia-reperfusion injury, and to investigate the mechanism by which DHA regulates microglia polarization. We administered DHA 5mg/kg intraperitoneally daily for 3 d following a transient middle cerebral artery occlusion reperfusion model in rats. The protective effects of DHA on cerebral ischemia-reperfusion injury were detected by TTC staining, HE staining, Nissler staining, and TUNEL staining. Quantitative real-time PCR, immunofluorescence, western blot, and enzyme-linked immunosorbent assay were used to detect the expression of M1 and M2 microglia-associated markers and PPARγ-mediated ERK/AKT signaling pathway proteins. We found that DHA significantly improved brain injury by decreasing the expression of the M1 phenotypic marker (iNOS, CD16) and increasing the expression of the M2 phenotypic marker (Arg-1, CD206). DHA also increased the expression of peroxisome proliferator-activated receptor gamma (PPARγ) mRNA and protein, increased the expression of the pathway protein AKT, and decreased the expression of ERK1/2. In addition, DHA promoted the expression of anti-inflammatory factor IL-10 and decreased the expression of pro-inflammatory factors TNF-α and IL-1β. However, the PPARγ antagonist GW9662 greatly blocked these beneficial effects. These results suggest that DHA may activate PPARγ to inhibit ERK and activate AKT signaling pathways to regulate microglia polarization, thereby reducing neuroinflammation and promoting neurological recovery to alleviate cerebral ischemia-reperfusion injury.

Treatment with 1,25-Dihydroxyvitamin D3 Delays Choroid Plexus Infiltration and BCSFB Injury in MRL/lpr Mice Coinciding with Activation of the PPARγ/NF-κB/TNF-α Pathway and Suppression of TGF-β/Smad Signaling

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a serious complication of systemic lupus erythematosus (SLE) involving the nervous system with high morbidity and mortality. A key hypothesis in NPSLE is that a disrupted barrier allows autoantibodies and immune components of peripheral blood to penetrate into the central nervous system (CNS), resulting in inflammation and damage. The blood cerebrospinal fluid barrier (BCSFB), which consists of the choroid plexus and the hypothalamic tanycytes, has long been regarded as an immunological sanctuary site. 1,25-Dihydroxyvitamin D3 [1,25-(OH)₂D₃] is the active form of vitamin D, which plays multiple roles in inflammation and immunoregulation. In this study, we investigated the possible protective effects of 1,25-dihydroxyvitamin D3 against BCSFB dysfunction in NPSLE in MRL/lpr mice and explored the mechanism by which 1,25-dihydroxyvitamin D3 inhibits the progression of NPSLE. In this study, we found that supplementation with 1,25-dihydroxyvitamin D3 markedly improved serological and immunological indices, delayed inflammatory infiltration, delayed neuronal deformation, and upregulated the expression of brain-derived neurotrophic factor (BDNF) proteins in the brain. Furthermore, 1,25-dihydroxyvitamin D3 downregulated proinflammatory cytokines such as nuclear factor kappa-B (NF-κB) and tumor necrosis factor-α (TNF-α) by activating peroxisome proliferator-activated receptor γ (PPARγ), and it reduced the expression of the TGF-β/Smad signaling pathway. Our findings demonstrate that 1,25-dihydroxyvitamin D3 delayed cell infiltration into the choroid plexus and decreased markers suggestive of cognitive decline in MRL/lpr mice, and the mechanism may be related to protection against BCSFB disruption through activation of the anti-inflammatory PPARγ/NF-κB/TNF-α pathway as well as upregulation of BDNF and inhibition of the TGF-β/Smad signaling pathway. These findings provide a novel direction for the study of NPSLE.

Microglia/macrophages require vitamin D signaling to restrain neuroinflammation and brain injury in a murine ischemic stroke model

Vitamin D deficiency is associated with worse clinical outcomes after ischemic stroke; nevertheless, the pathophysiological mechanisms remain largely unexplored. In this study, we characterized the molecular mechanisms of how vitamin D signaling modulated stroke progression in male mouse ischemia-reperfusion stroke models. We found that vitamin D receptor (VDR) exhibited a predominant upregulation in peri-infarct microglia/macrophages following cerebral ischemia. Conditional Vdr inactivation in microglia/macrophages markedly augmented infarct volumes and neurological deficits. VDR-deficient microglia/macrophages exhibited a more primed proinflammatory phenotype with substantial secretion of TNF-α and IFN-γ. These inflammatory cytokines further enhanced CXCL10 release from endothelial cells and blood-brain barrier disruption, and ultimately infiltration of peripheral T lymphocytes. Notably, blocking TNF-α and IFN-γ significantly ameliorated stroke phenotypes in Vdr conditional knockout mice. Collectively, VDR signaling in microglia/macrophages plays a crucial role in restraining ischemia-elicited neuroinflammation and stroke progression. Our findings delineate a novel mechanism underlying the association between vitamin D deficiency and poor stroke outcomes, and underline the significance of maintaining a functional vitamin D signaling in the management of acute ischemic stroke.

Vitamin D Enhances Hematoma Clearance and Neurologic Recovery in Intracerebral Hemorrhage

BACKGROUND

Erythrophagocytosis by reparative monocyte-derived macrophage contributes to hematoma clearance and neurological recovery after intracerebral hemorrhage (ICH). Vitamin D (VitD) is a neuroprotective hormone and regulates the differentiation of monocyte-derived macrophage from monocytes. In this study, we examined the effects of VitD supplementation on monocyte-derived macrophage and hematoma clearance in rodent with ICH.

METHODS

Neurobehavioral functions and hematoma volume were assessed using a collagenase injection model in both young- and middle-aged mice with or without VitD treatment given 2 hours post-ICH induction. We used flow cytometry to analyze CD36 expression and macrophage and undifferentiated monocyte cell numbers during in vivo erythrophagocytosis in collagenase and autologous blood injection models. Western blot analysis and immunofluorescence were used to assess the expression levels of the PPAR-γ (peroxisome proliferator-activated receptor γ)-CD36 axis and CD206. A macrophage differentiation study was conducted on murine bone marrow-derived monocytes.

RESULTS

VitD promoted neurological recovery and facilitated hematoma clearance in both young- and middle-aged mice after ICH. Within the perihematomal region, mature macrophages, rather than undifferentiated monocytes, expressed higher levels of CD36 in driving erythrocyte clearance. VitD increased the macrophage number but decreased the monocyte number and elevated the levels of CD36 and PPAR-γ in the brain. In vitro, VitD accelerated the differentiation of reparative macrophages from bone marrow-derived monocytes.

CONCLUSIONS

VitD promotes reparative macrophage differentiation, facilitates hematoma clearance, and improves neurobehavioral performance in mice with ICH, suggesting that VitD should be further examined as a potentially promising treatment for ICH.

Role of JAK-STAT and PPAR-Gamma Signalling Modulators in the Prevention of Autism and Neurological Dysfunctions

The Janus-kinase (JAK) and signal transducer activator of transcription (STAT) signalling pathways regulate gene expression and control various factors involved in normal physiological functions such as cell proliferation, neuronal development, and cell survival. JAK activation phosphorylates STAT3 in astrocytes and microglia, and this phosphorylation has been linked to mitochondrial damage, apoptosis, neuroinflammation, reactive astrogliosis, and genetic mutations. As a regulator, peroxisome proliferator-activated receptor gamma (PPAR-gamma), in relation to JAK-STAT signalling, prevents this phosphorylation and aids in the treatment of the above-mentioned neurocomplications. Changes in cellular signalling may also contribute to the onset and progression of autism. Thus, PPAR-gamma agonist upregulation may be associated with JAK-STAT signal transduction downregulation. It may also be responsible for attenuating neuropathological changes by stimulating SOCS3 or involving RXR or SMRT, thereby reducing transcription of the various cytokine proteins and genes involved in neuronal damage. Along with JAK-STAT inhibitors, PPAR-gamma agonists could be used as target therapeutic interventions for autism. This research-based review explores the potential involvement and mutual regulation of JAK-STAT and PPAR-gamma signalling in controlling multiple pathological factors associated with autism.

1α,25-Dihydroxyvitamin D3 Promotes Angiogenesis After Cerebral Ischemia Injury in Rats by Upregulating the TGF-β/Smad2/3 Signaling Pathway

Stroke is a disease with high morbidity, disability and mortality, which seriously endangers the life span and quality of life of people worldwide. Angiogenesis and neuroprotection are the key to the functional recovery of penumbra function after acute cerebral infarction. In this study, we used the middle cerebral artery occlusion (MCAO) model to investigate the effects of 1α,25-dihydroxyvitamin D3 (1,25-D3) on transforming growth factor-β (TGF-β)/Smad2/3 signaling pathway. Cerebral infarct volume was measured by TTC staining. A laser speckle flow imaging system was used to measure cerebral blood flow (CBF) around the ischemic cortex of the infarction, followed by platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) and isolectin-B4 (IB4) immunofluorescence. The expression of vitamin D receptor (VDR), TGF-β, Smad2/3, p-Smad2, p-Smad3, and vascular endothelial growth factor (VEGF) was analyzed by western blot and RT-qPCR. Results showed that compared with the sham group, the cerebral infarction volume was significantly increased while the CBF was reduced remarkably in the MCAO group. 1,25-D3 reduced cerebral infarction volume, increased the recovery of CBF and expressions of VDR, TGF-β, p-Smad2, p-Smad3, and VEGF, significantly increased IB4⁺ tip cells and CD31⁺ vascular length in the peri-infarct area compared with the DMSO group. The VDR antagonist pyridoxal-5-phosphate (P5P) partially reversed the neuroprotective effects of 1,25-D3 described above. In summary, 1,25-D3 plays a neuroprotective role in stroke by activating VDR and promoting the activation of TGF-β, which in turn up-regulates the TGF-β/Smad2/3 signaling pathway, increases the release of VEGF and thus promotes angiogenesis, suggesting that this signaling pathway may be an effective target for ischemic stroke treatment. 1,25-D3 is considered to be a neuroprotective agent and is expected to be an effective drug for the treatment of ischemic stroke and related diseases.

Nuclear Receptors in Myocardial and Cerebral Ischemia-Mechanisms of Action and Therapeutic Strategies

Nearly 18 million people died from cardiovascular diseases in 2019, of these 85% were due to heart attack and stroke. The available therapies although efficacious, have narrow therapeutic window and long list of contraindications. Therefore, there is still an urgent need to find novel molecular targets that could protect the brain and heart against ischemia without evoking major side effects. Nuclear receptors are one of the promising targets for anti-ischemic drugs. Modulation of estrogen receptors (ERs) and peroxisome proliferator-activated receptors (PPARs) by their ligands is known to exert neuro-, and cardioprotective effects through anti-apoptotic, anti-inflammatory or anti-oxidant action. Recently, it has been shown that the expression of aryl hydrocarbon receptor (AhR) is strongly increased after brain or heart ischemia and evokes an activation of apoptosis or inflammation in injury site. We hypothesize that activation of ERs and PPARs and inhibition of AhR signaling pathways could be a promising strategy to protect the heart and the brain against ischemia. In this Review, we will discuss currently available knowledge on the mechanisms of action of ERs, PPARs and AhR in experimental models of stroke and myocardial infarction and future perspectives to use them as novel targets in cardiovascular diseases.

Influence of the Bioactive Diet Components on the Gene Expression Regulation

Diet bioactive components, in the concept of nutrigenetics and nutrigenomics, consist of food constituents, which can transfer information from the external environment and influence gene expression in the cell and thus the function of the whole organism. It is crucial to regard food not only as the source of energy and basic nutriments, crucial for living and organism development, but also as the factor influencing health/disease, biochemical mechanisms, and activation of biochemical pathways. Bioactive components of the diet regulate gene expression through changes in the chromatin structure (including DNA methylation and histone modification), non-coding RNA, activation of transcription factors by signalling cascades, or direct ligand binding to the nuclear receptors. Analysis of interactions between diet components and human genome structure and gene activity is a modern approach that will help to better understand these relations and will allow designing dietary guidances, which can help maintain good health.

Mechanism of neuroprotective effect of stevioside on cerebral ischemia-reperfusion injury via PPAR-γ activation

OBJECTIVE

The aim of this work was to explore the possible protective effects and its mechanism of stevioside on cerebral ischemia reperfusion (CIR) induced neuron damages.

METHODS

Middle cerebral artery occlusion/reperfusion (MCAO/R) rat models were constructed. The rats were treated with stevioside treatment, PPAR-γ antagonist GW9662, PPAR-γ activator pioglitazone or PI3K/AKT inhibitor LY294002 before neurological deficits were assessed using modified Neurological Severity Scale (mNSS) scores. The infarct size, brain injury, apoptotic cells, inflammatory cytokines in neurons extracted from MCAO/R rats were determined by TTC staining, H&E staining, TUNEL staining, qRT-PCR and Western blot, respectively.

RESULTS

Stevioside attenuates MCAO/R-induced neuronal apoptosis and inflammation by regulating PPAR-γ expression. Besides, PPAR-γ activates PI3K/AKT signaling pathway. Moreover, PPAR-γ antagonist GW9662 or PI3K/AKT inhibitor LY294002 abrogated the anti-apoptosis and anti-inflammatory effects of stevioside on MCAO/R rats.

CONCLUSION

Stevioside alleviates MCAO/R-induced neuronal apoptosis and inflammation by upregulating PPAR-γ to activate PI3K/AKT signaling pathway.

Immune Cells in the BBB Disruption After Acute Ischemic Stroke: Targets for Immune Therapy?

Blood-Brain Barrier (BBB) disruption is an important pathophysiological process of acute ischemic stroke (AIS), resulting in devastating malignant brain edema and hemorrhagic transformation. The rapid activation of immune cells plays a critical role in BBB disruption after ischemic stroke. Infiltrating blood-borne immune cells (neutrophils, monocytes, and T lymphocytes) increase BBB permeability, as they cause microvascular disorder and secrete inflammation-associated molecules. In contrast, they promote BBB repair and angiogenesis in the latter phase of ischemic stroke. The profound immunological effects of cerebral immune cells (microglia, astrocytes, and pericytes) on BBB disruption have been underestimated in ischemic stroke. Post-stroke microglia and astrocytes can adopt both an M1/A1 or M2/A2 phenotype, which influence BBB integrity differently. However, whether pericytes acquire microglia phenotype and exert immunological effects on the BBB remains controversial. Thus, better understanding the inflammatory mechanism underlying BBB disruption can lead to the identification of more promising biological targets to develop treatments that minimize the onset of life-threatening complications and to improve existing treatments in patients. However, early attempts to inhibit the infiltration of circulating immune cells into the brain by blocking adhesion molecules, that were successful in experimental stroke failed in clinical trials. Therefore, new immunoregulatory therapeutic strategies for acute ischemic stroke are desperately warranted. Herein, we highlight the role of circulating and cerebral immune cells in BBB disruption and the crosstalk between them following acute ischemic stroke. Using a robust theoretical background, we discuss potential and effective immunotherapeutic targets to regulate BBB permeability after acute ischemic stroke.

Curcumin ameliorates ischemic stroke injury in rats by protecting the integrity of the blood-brain barrier

The blood-brain barrier (BBB) is critical for proper cerebral homeostasis and its dysfunction during ischemic stroke can result in significant neurological injury. The major goal of the present study was to identify whether curcumin pretreatment possessed protective effects on BBB integrity during the 24 h of acute ischemic brain injury. To investigate the protective effects of curcumin, male Sprague-Dawley rats were divided into multiple groups, including sham, middle cerebral artery occlusion/reperfusion (MCAO/R) vehicle and curcumin pretreated MCAO/R groups. The effects of curcumin were measured by analyzing neurological deficits, infarct size, BBB permeability and expression levels of permeability-related proteins in the brain. It was found that curcumin pretreatment significantly improved neurological scores, decreased infarct size, and protected synaptic remodeling of hippocampal neurons and upregulated the protein expression level of tight junction proteins, ZO-1, occludin and claudin-5 in ischemic rat brains. Furthermore, curcumin pretreatment before stroke was shown to downregulate the phosphorylation of NF-κB and MMP-9, which are central mediators of inflammation. The results from the present study indicated that curcumin pretreatment ameliorated ischemic stroke injury by protecting BBB integrity and synaptic remodeling, as well as inhibiting inflammatory responses.

PPARγ in Ischemia-Reperfusion Injury: Overview of the Biology and Therapy

Ischemia-reperfusion injury (IRI) is a complex pathophysiological process that is often characterized as a blood circulation disorder caused due to various factors (such as traumatic shock, surgery, organ transplantation, burn, and thrombus). Severe metabolic dysregulation and tissue structure destruction are observed upon restoration of blood flow to the ischemic tissue. Theoretically, IRI can occur in various tissues and organs, including the kidney, liver, myocardium, and brain, among others. The advances made in research regarding restoring tissue perfusion in ischemic areas have been inadequate with regard to decreasing the mortality and infarct size associated with IRI. Hence, the clinical treatment of patients with severe IRI remains a thorny issue. Peroxisome proliferator-activated receptor γ (PPARγ) is a member of a superfamily of nuclear transcription factors activated by agonists and is a promising therapeutic target for ameliorating IRI. Therefore, this review focuses on the role of PPARγ in IRI. The protective effects of PPARγ, such as attenuating oxidative stress, inhibiting inflammatory responses, and antagonizing apoptosis, are described, envisaging certain therapeutic perspectives.

Evans Blue Might Produce Pathologically Activated Neuroprotective Effects via the Inhibition of the P2X4R/p38 Signaling Pathway

The main pathological features of ischemic stroke include neuronal damage and blood-brain barrier (BBB) dysfunction. Previous studies have shown that Evans Blue, a dye used to probe BBB integrity, could enter the brain only during the pathological status of ischemic stroke, indicating the potential pathologically activated therapeutic use of this chemical to treat ischemic stroke. In this study, we have reported that Evans Blue could produce in vitro neuroprotective effects against iodoacetic acid (IAA)-induced hypoxia neuronal death in HT22 cells. We further found that P2X purinoreceptor 4 (P2X4R), a subtype of ATP-gated cation channel, was expressed in HT22 cells. Evans Blue could prevent IAA-induced increase of P2X4R mRNA and protein expression. Interestingly, shRNA of P2X4R could protect against IAA-induced activation of p38, and SB203580, a specific inhibitor of p38, could reverse IAA-induced neurotoxicity, indicating that p38 is a downstream signaling molecule of P2X4R. Molecular docking analysis further demonstrated the possible interaction between Evans Blue and the ATP binding site of P2X4R. Most importantly, pre-treatment of Evans Blue could largely reduce neurological and behavioral abnormity, and decrease brain infarct volume in middle cerebral artery occlusion/reperfusion (MCAO) rats. All these results strongly suggested that Evans Blue could exert neuroprotective effects via inhibiting the P2X4R/p38 pathway, possibly by acting on the ATP binding site of P2X4R, indicating that Evans Blue might be further developed as a pathologically activated therapeutic drug against ischemic stroke.

Microglial/Macrophage polarization and function in brain injury and repair after stroke

Stroke is a leading cause of disability and mortality, with limited treatment options. After stroke injury, microglia and CNS‐resident macrophages are rapidly activated and regulate neuropathological processes to steer the course of functional recovery. To accelerate this recovery, microglia can engulf dying cells and clear irreparably‐damaged tissues, thereby creating a microenvironment that is more suitable for the formation of new neural circuitry. In addition, monocyte‐derived macrophages cross the compromised blood‐brain barrier to infiltrate the injured brain. The specific functions of myeloid lineage cells in brain injury and repair are diverse and dependent on phenotypic polarization statuses. However, it remains to be determined to what degree the CNS‐invading macrophages occupy different functional niches from CNS‐resident microglia. In this review, we describe the physiological characteristics and functions of microglia in the developing and adult brain. We also review (a) the activation and phenotypic polarization of microglia and macrophages after stroke, (b) molecular mechanisms that control polarization status, and (c) the contribution of microglia to brain pathology versus repair. Finally, we summarize current breakthroughs in therapeutic strategies that calibrate microglia/macrophage responses after stroke.

The present review summarizes recent advances in microglial research in relation to stroke with emphases on microglial/macrophage phenotypic polarization and function in brain injury and repair. It also reviews the physiological characteristics and functions of microglia in the developing and adult brain, and describes current breakthroughs in therapeutic strategies that calibrate microglia/macrophage responses after stroke.

4-Methoxybenzylalcohol protects brain microvascular endothelial cells against oxygen-glucose deprivation/reperfusion-induced injury via activation of the PI3K/AKT signaling pathway

Damage to the blood-brain barrier (BBB) during the process of cerebral ischemic injury is a key factor that affects the treatment of this condition. The present study aimed to assess the potential effects of 4-methoxybenzyl alcohol (4-MA) on brain microvascular endothelial cells (bEnd.3) against oxygen-glucose deprivation/reperfusion (OGD/Rep) using an in vitro model that mimics in vivo ischemia/reperfusion injury. In addition, the present study aimed to explore whether this underlying mechanism was associated with the inhibition of pro-inflammatory factors and the activation status of the PI3K/Akt signaling pathway. bEnd.3 cells were subjected to OGD/Rep-induced injury before being treated with 4-MA, following which cell viability, lactate dehydrogenase (LDH) release and levels of nitric oxidase (NO) were detected by colorimetry, pro-inflammatory factors including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6, were detected by ELISA. The expression levels of occluding and claudin-5were evaluated by immunofluorescence staining. The expression levels of AKT, phosphorylated (p)-Akt, endothelial nitric oxide synthase (eNOS) and p-eNOS were also measured by western blot analysis. After bEnd.3 cells were subjected to OGD/Rep-induced injury, cell viability and NO levels were significantly decreased, whilst LDH leakage and inflammatory factor (TNF-α, IL-1β and IL-6) levels were significantly increased. Treatment with 4-MA significantly ameliorated cell viability, LDH release and the levels of NO and pro-inflammatory factors TNF-α, IL-1β and IL-6 as a result of OGD/Rep. Furthermore, treatment with 4-MA upregulated the expression of occludin, claudin-5, Akt and eNOS, in addition to increasing eNOS and AKT phosphorylation in bEnd.3 cells. These results suggest that 4-MA can alleviate OGD/Rep-induced injury in bEnd.3 cells by inhibiting inflammation and by activating the PI3K/AKT signaling pathway as a possible mechanism. Therefore, 4-MA can serve as a potential candidate for treating OGD/Rep-induced injury.

Protection against acute cerebral ischemia/reperfusion injury by Leonuri Herba Total Alkali via modulation of BDNF-TrKB-PI3K/Akt signaling pathway in rats

OBJECTIVE

To observe the brain protective effect of Leonuri Herba Total Alkali (LHA) on cerebral ischemia reperfusion injury in rats, so as to provide basis for clinical research.

METHODS

Adult male SD rats were randomly assigned into sham group, middle cerebral artery occlusion/reperfusion (MCAO/R) group, and LHA + MCAO/R group (25 mg/kg, 50 mg/kg, and 100 mg/kg). Fourteen days before MCAO/R surgery, the rats in treatment groups were orally administered with LHA in ultrapure water once daily for 14 days, while rats in the sham and MCAO groups were given the same amount of saline in advance. After 1 h of administration on the 14th day, MCAO surgery was subjected. The neurological deficits, brain infarct volume, histopathology, immunofluorescence, inflammation indicators and the gene/protein expressions of BDNF-TrKB-PI3K/Akt signaling pathway in the rat brain tissue were evaluated 24 h after the MCAO/R-injury.

RESULTS

It was found that rats in LHA pre-administration group showed significantly reduced neurological deficit scores, infarction volume, the serum levels of NSE and S100β. Meanwhile, the content of Evans Blue (EB) in brain tissue from LHA group was decreased, as well as the levels of inflammatory cytokines and their gene levels. Moreover, LHA pre-administration inhibited the expression of CD44, GFAP, FOXO1 and promoted the expression of BDNF and NeuN. In addition, LHA pre-administration could up-regulate the protein expression of TrkB, p-PI3K, p-Akt, Bcl-2, and down-regulate the protein expression of Bax, and increase the level of Bcl-2/Bax.

CONCLUSIONS

The study demonstrated that LHA pre-administration could regulate the PI3K/Akt pathway by increasing BDNF levels, and play a neuroprotective role in cerebral ischemia-reperfusion injury.

Preoperative Serum Level of Vitamin D is a Possible Protective Factor for Peritumoral Brain Edema of Meningioma: A Cross Sectional Study

Meningioma is associated with the development of vasogenic edema defined as disrupted blood brain barrier. Vitamin D3 through its own nuclear receptor can regulate the expression of many effective agents on the integrity of the blood brain barrier. This study aimed to investigate the association between preoperative serum levels of 25(OH)D and peritumoral brain edema in patients with meningioma. One hundred and twelve patients with meningioma completed the study. Serum 25(OH)D levels assessment and magnetic resonance imaging (MRI) were done for all patients at the beginning of the study. The percentage of edema index (EI) was used to estimate the extent of peritumoral brain edema through preoperative MRI. The median serum level of 25(OH)D in the patients with the percentage of EI < 100% was significantly higher than those with > 100% (65.58 vs. 37.33, P < 0.001). The median percentage of EI was 24.9. Preoperative serum levels of 25(OH)D had an inverse and significant correlation with the percentage of EI as by increasing each 1 ng/mL of serum 25(OH)D, EI was decreased approximately 4% (95% CI; -5.984 to -1.952, P < 0.001). Vitamin D may be a protective factor for peritumoral brain edema of meningioma.

Post-Ischaemic Immunological Response in the Brain: Targeting Microglia in Ischaemic Stroke Therapy

Microglia, the major endogenous immune cells of the central nervous system, mediate critical degenerative and regenerative responses in ischaemic stroke. Microglia become "activated", proliferating, and undergoing changes in morphology, gene and protein expression over days and weeks post-ischaemia, with deleterious and beneficial effects. Pro-inflammatory microglia (commonly referred to as M1) exacerbate secondary neuronal injury through the release of reactive oxygen species, cytokines and proteases. In contrast, microglia may facilitate neuronal recovery via tissue and vascular remodelling, through the secretion of anti-inflammatory cytokines and growth factors (a profile often termed M2). This M1/M2 nomenclature does not fully account for the microglial heterogeneity in the ischaemic brain, with some simultaneous expression of both M1 and M2 markers at the single-cell level. Understanding and regulating microglial activation status, reducing detrimental and promoting repair behaviours, present the potential for therapeutic intervention, and open a longer window of opportunity than offered by acute neuroprotective strategies. Pharmacological modulation of microglial activation status to promote anti-inflammatory gene expression can increase neurogenesis and improve functional recovery post-stroke, based on promising preclinical data. Cell-based therapies, using preconditioned microglia, are of interest as a method of therapeutic modulation of the post-ischaemic inflammatory response. Currently, there are no clinically-approved pharmacological options targeting post-ischaemic inflammation. A major developmental challenge for clinical translation will be the selective suppression of the deleterious effects of microglial activity after stroke whilst retaining (or enhancing) the neurovascular repair and remodelling responses of microglia.